Significant associations of HLA-B*5101 and B*5108, and lack of association of class II alleles with Behçet's disease in Italian patients

HLA class I genotyping including HLA-B*51 allele typing in the Iranian patients with Behçet's disease

It is well known that Behçet's disease (BD) is strongly associated with human leukocyte antigen (HLA) B51 in many ethnic groups. However, there has been no published report as yet with respect to this association among the Iranian people. Furthermore, since it is now known that the B51 antigen can be encoded by 21 alleles, B*5101-B*5121, we performed HLA-B*51 allele typing as well as HLA class I genotyping of 48 Iranian patients with this disease. As a result, the frequency of the B*51 allele was significantly higher (62.1%) in the patient group as compared with the ethnically matched control group (31.8%) (Pc=0.067, R.R.=3.51). In the genotyping of B*51 alleles, 33 out of the 36 B*51-positive patients possessed B*5101 and the remaining 3 carried B*5108. This study revealed that Iranian patients with BD also had a strong association with HLA-B51. In addition, this significantly high incidence of HLA-B*51 was found to be caused by an increase in both the HLA-B*5101 and HLA-B*5108 alleles. However, there was no significant difference in the HLA-B*51 allelic distribution between the patient and control groups.

Behçet disease

Behçet's disease is a multisystem inflammatory disorder of unknown origin, characterized by recurrent oral and genital ulcerations, ocular and cutaneous lesions, arthritis, central nervous system, and vascular disease. There is no pathognomonic laboratory test, but there are clinical criteria to assist in establishing the diagnosis. Behçet's is most common along the Silk Road. It is particularly common among persons who have the HLA-B51 major histocompatibility type. Cutaneous lesions include pustules, erythema nodosum-like lesions, Sweet's-like lesions, pyoderma gangrenosum-ike lesions, and pathergy. The major cutaneous findings may be classified as neutrophilic vascular reactions. There is considerable morbidity resulting from Behçet's disease, most notably a high risk of blindness from ocular involvement. Mortality may occur as a result of neurologic or vascular disease or gastrointestinal perforation.

HLA-B*51 and B*15 alleles confer predisposition to Behçet's disease in Moroccan patients

HLA class I polymorphism in Moroccan patients with Behçet's disease has not been investigated so far. In this study, HLA-B* phenotype frequencies were analyzed in 86 unrelated Moroccan patients (45 males, 41 females) and 111 ethnically matched healthy controls. The predisposing effect of the B*51 was confirmed (30.2% in patients and 15.3% in controls, OR = 2.39, 95% CI [1.2-4.8], p = 0.015). It was mostly observed in males with young age at disease onset (OR= 5.5 [1.9-15.9], p = 0.002 compared to controls). The Moroccan BD group also presented a previously unknown association with HLA-B*15 (25.6% of patients versus 11.7% of controls, OR = 2.59 [1.2-5.5], p = 0.014), both in females and in males with late-onset of the disease. Altogether, the B*15 and/or B*51 alleles were expressed in 55.8% of patients compared to 27% of controls (OR = 3.4 [1.9-6.2], p < 10-4, Pc = 0.003). Our data indicate HLA-B effects on BD pathogenesis should be considered separately for men and women.

Behçet disease

Central nervous system involvement in Behçet disease (BD) may be either parenchymal or nonparenchymal. Abnormal cerebrospinal fluid findings and parenchymal involvement are associated with a poorer prognosis. A self-antigenic role for HLA B51 has been postulated in the pathogenesis of BD. The sibling occurrence rate is 3.6%. Familial aggregation may be more pronounced among pediatric cases compared with adult cases. The importance of inherited coagulation abnormalities in the pathogenesis of BD is not clear. Vasculitis of the vasa vasorum seems to be the major site of pathology in large vessel disease. Even among experts, no consensus exists regarding the optimal approach to treatment. Low-dose thalidomide is effective for the mucocutaneous lesions, but polyneuropathy complicates its prolonged use. Neurologic side effects of cyclosporine A should preclude its use in patients with central nervous system involvement except in unusual circumstances. The heightened inflammatory response of BD patients to simple trauma may lead to postoperative complications, but should not be regarded as a contraindication to surgery.